- The return of old characters (e.g. Medivh, Alleria and Turalyon)
- Emerald Dream / Azshara / Burning Legion / South Seas / Titans themes
- Less lore-focus on the humain / orcs, more on the other races / capitals / towns
- More zones involved that already exists (Kul'Tiras, Under Tirisfal...etc)
- Revamped Outland (Draenei and Blood Elf zones) to catch up with the lore (e.g using closed portals to visit the Burning Legions' world(s))
- A little rework to Northrend to reflect the new Lich King changes
- Lore-book aLa dungeons codex, we can also track stories from the quests we do

Class

- Class book similar to dungeon codex : more info on the lore, spells...etc
- 4th spec (unlikely)
- Search feature in spell-books
- More separated spell for PvP and PvE
- Less class homogenization
- Bring back the good old class quests
- More cosmetic glyphs

Mage :

- Female water elemental (glyph or spell)

Warlock :

- Viable tanking
- Renaming of pets
- Flying wings (flying mount)

Death Knight :

- Dual Wield in every spec

Rogue :

- Combo points on the rogue (unlikely, unless they rework a lot of things)
- Make Pickpocketing more fun / worth

- PvP servers with no flying mounts (after dismounting in a contested zone)
- Solo Queue for Rated Battlegrounds
- More World PvP zones
- 1 Versus 1 Rated Arenas
- PvP daillies with fun objectives and better rewards than the normal BG dailies (kill 10 elfs / mages / in less than 5 mins for eg)
- PvP rewards only obtainable in World PvP
- PvP Scenarios
- Players can now be dismounted while flying (parachuted to the ground or no fall damage) so flying will be no more 100% safe
- New game mods for arena : like 4 tigers attached that attacks random players from time to time (SPARTAAAAAAAAAAAAAA)
- Bring back PvP ranks with a little rework and statistics (e.g Season kills / rbgs / arenas) http://www.wowwiki.com/Honor_system_%28pre-2.0%29
- Captcha / Visual logging...etc before you enter battlegrounds = less botting

PvE

- Healing Target Dummy
- 10 levels expansion
- Scenarios available at low level
- Old Lore scenarios (e.g Battle for the Undercity)
- Leveling Modes : slow leveling without any XP buffs (guild perk, heirloom ...ect) and a fast leveling for those with 5 characters already at max level
- Karazhan readjusted lore and mechanics (ala Scholomance). Medivh helping you reclaiming his old tower can an eminent point for his return (unlikely)
- Multiple starting zones
- Harder heroics
- Upgradeable Weapons / Armors
- Groups quests
- More Environment incidence on the players : Cold zones will make run at a slower speed , Heat zones will get you exhausted, Creepy zones will make you fear and run ...etc
- Day / Night cycle

I will keep updating the post with so and try to give more detailed ideas

Damage from abilities able to be different in pvp from pve. So they can somehow be individually balanced.
They did it with some abilites, i just dont understand they dont go all nine yards. Get rid of this endless pve / pvp "balance" crusade.

Demon hunter Hero Class(this is a deal breaker for me so yeah)
Illidan back as a good guy
New char models(don't really care much but ppl seem to want them so what the hey)
Maybe a new demonic race but meh
Burning Legion of hell !!!

You think I'm kidding, but I'm not. I want a damn sandwich! All that meat and bread and cheese in every city but nobody's thought of putting it together. Let me make custom sandwiches, nonstackable, no-buff food, and I'm a happy tank.

-gut LFR.
-openraid style system implemented onsite, not in game(takes a lot of space for sure)
-gear check bosses, so at least some farming has to be done or progression
-scenarios only for leveling 1-levelcap. MMOs without the trinity don't do well
-resil decay (as gear goes up resil goes down)
-world bosses AND Baradin Hold VoA style, the latter for tier
-same personal legendary, but requiring at least some heroic or end normal kill
-valor as a chatchup for raiders, not free upgrades for dungeon-ers
-way to keep alt runs of old tier relevant(goes with no LFR)
-Cata level heroics
-new mail class
-dailies, grind and dynamic events at cap, but without hating rep behind rep
-AV and IoC warfront idea implemented
-transmog heirlooms
-accounwide PvP mounts, titles an access to armor
-account wide challenge mode mounts titles access to armor
-less racey chain pull challenge modes
-some way to get old PvP armor and weapons, removed ones added back, possibly a way to get old elite armor (get rating in curren season)
-(unlikely) flying mounts slowed below ground mounts. Can get around faster on ground, but at risk. Flying slower but safer.